Constipation: A physiological approach - CORE

Constipation:A physiological approach

W Grant Thompson MD

Constipation is a very common complaint in primarycare and gastroenterology practice. It is said to be pres-

ent in 1% to 8% of the population (1-5), but these figures arevery much subject to how one defines constipation. Indeed,Probert et al (2) found that constipation was present inabout 60 (8%) of 731 randomly selected women, defined bypatient complaint, expert opinion (Rome criteria, Table 1)

(6,7) or stool form as a surrogate measure of transit time(vide infra). However, these definitions each selected a dif-ferent 60 people. Only 17 women were constipated accord-ing to all three definitions. These data show the importanceof determining in detail what the patient means by ‘constip-ation’ and the need to interpret his or her symptoms inphysiological terms. In this paper, stool and the colorectal

Can J Gastroenterol Vol 14 Suppl D November 2000 155D

This review was prepared from a presentation made at the Canadian Association of Gastroenterology Meeting, Banff, Alberta, March 1 to 8, 1998.Division of Gastroenterology, University of Ottawa, Ottawa, OntarioCorrespondence: Dr W Grant Thompson, Emeritus Professor of Medicine, University of Ottawa, 7 Nesbitt Street, Ottawa, Ontario, K2H 8C4.

Telephone 613-828-7300, fax 613-828-7300, e-mail [email protected]

MINI-REVIEW

WG Thompson. Constipation: A physiological approach. Can JGastroenterol 2000;14(Suppl D):155D-162D. The first step inmanaging a patient with constipation is to understand the precisenature of the complaint. Is the onset recent? What are the fre-quency and form of the stools, and how much effort is required todefecate? Is constipation steady or alternating as in irritable bowelsyndrome? Are there structural, metabolic or pharmacologicalconfounders? Is the patient depressed? Has dietary fibre been triedat a sufficient dose? What are the patient’s understanding and be-liefs about the symptoms? Has there been sufficient and appropri-ate investigation? Armed with the answers to these questions,physicians can help most patients through lifestyle, dietary andpharmacological adjustments, along with supplementary fibre.Some patients may require regular doses of an osmotic laxative.Those few that fail these measures should have their transit timeestimated while on a high fibre diet; if it is normal, further testingis unlikely to help. The above efforts should be re-emphasized, andreassurance should be offered. Some patients may require a psy-chological assessment. If transit time is prolonged and the patientmay benefit from surgery for colonic inertia or biofeedback for an-ismus, then colon and anorectal function should be assessed. Thedecision to perform further tests should be made carefully, and un-realistic expectations should be discouraged. Before surgery is of-fered, the patient should have the benefit of receiving an expertopinion. Biofeedback helps some patients with isolated anorectaldysfunction.

Key Words: Anorectal function; Colon; Colon physiology; Consti-

pation; Stools; Transit time

Constipation : approche physiologiqueRÉSUMÉ : La première étape à franchir dans le traitement de la constipa-tion est de circonscrire la nature des symptômes. Sont-ils d’apparition ré-cente? Quelles sont la fréquence et la forme des selles, et quelle intensitéd’effort la défécation exige-t-elle? La constipation est-elle permanente ouépisodique comme dans le cas du syndrome du côlon irritable? Y a-t-il desfacteurs confusionnels liés aux structures, au métabolisme ou à la prise demédicaments? Le patient est-il déprimé? A-t-il essayé un régime alimen-taire suffisamment riche en fibres alimentaires? Comment le patient inter-prète-t-il ses symptômes? Les symptômes ont-ils fait l’objet d’uneévaluation appropriée? Munis des réponses à ces questions, les médecinssont en mesure d’aider la plupart des patients par des interventions tou-chant le mode de vie, le régime alimentaire et la prise de médicaments; àcela s’ajoute un complément de fibres. Certains patients peuvent avoir be-soin régulièrement de laxatifs osmotiques. Dans les rares cas d’échec dutraitement, le temps de transit devrait être évalué pendant que les patientssuivent un régime riche en fibres; si le temps est normal, il est peu probableque d’autres examens puissent apporter un soulagement quelconque. Il fau-drait insister de nouveau sur les interventions précédentes et rassurer lespatients. Certains d’entre eux devront être soumis à une évaluation psy-chologique. Si le temps de transit est prolongé et si une intervention chi-rurgicale pour inertie du côlon ou la rétroaction biologique pour anismuspeuvent s’avérer bénéfiques, il faudrait procéder à une évaluation du fonc-tionnement du côlon, du rectum et de l’anus. La décision de poursuivre lesexamens devrait être prise en connaissance de cause, et il faudrait tempérerles attentes irréalistes. Le patient devrait avoir droit à l’avis d’un deuxièmemédecin avant qu’on lui propose l’intervention chirurgicale. La rétroac-tion biologique peut aider parfois les patients souffrant de dysfonctionne-ment ano-rectal occasionnel.

physiology responsible for delivering it are discussed. Armedwith this information, a practical algorithm can be con-structed for primary care physicians and specialists who carefor patients with constipation.

THE STOOLConstipation cannot be understood without knowledge of thenature of stool. While the frequency of defecation is an impor-tant characteristic to consider, stool form (consistency) andthe effort needed to expel the stool are also important. Inphysiological terms, constipation is best measured by colontransit time, but it, in turn, is dependent on stool size and themotor prowess of the colon and anorectum.Determinants of stool size: Stool is the residue left over fromthe absorption of ingesta in the small intestine, and consistsmainly of bacteria, water and gas. Unabsorbed material islargely carbohydrate that is resistant to small intestinal en-zymes and subject to degradation by colon bacteria (8-10). Itseems that colon bacteria is acquired in infancy. The bacteriaremain for a lifetime and have a composition as unique to theindividual as fingerprints. These bacteria determine the extentand nature of the degradation of small bowel products and,therefore, must play an important role in determining stool sizeand composition, colon gas production and defecation. Littleis known about this process. The colon remains a dark conti-nent of clinical research, but the following facts are notable.

While all human colons produce varying amounts of hy-drogen and carbon dioxide (11), only one-third of colonsproduce methane – a result of the presence of Methanobacter

species (12) and dietary sulphate (13). These gases are im-portant determinants of stool volume and are a more likelycause of floating stools than fat content. Dietary bulk that es-capes bacterial degradation has water-holding propertiesthat help to determine stool size (14-16) and transit time(17,18). Particle size seems important: coarse bran, by resist-ing bacterial degradation, has a greater effect on stool weightand transit than fine bran (14).

Gastrointestinal transit time is related to the characteris-tics of the stool. A large stool traverses the colon faster, andthose on a high fibre diet have faster gut transits and less con-stipation (17). Slow transit increases the time available forcolonic water absorption, bacterial degradation and gas for-mation, thus fundamentally altering the stool form.

Even psychological and personality factors seem impor-tant. Extroverted, outgoing people have larger stools thanthose who are introverted (16). In contrast, stool size may bean important factor in the constipation that is seen so oftenin the depressed. These variables are important for the un-derstanding of constipation and may offer clues for effectivemanagement.Stool form: When considering a complaint of constipation(or diarrhea), stool form or consistency is more importantthan frequency. Many misperceptions about constipationcan be resolved if a detailed description of the stools is ob-tained. Patients may claim that the frequent production ofpellety stools is diarrhea, even though such stools are associ-ated with prolonged colonic transit (19-21). This has beentermed ‘pseudodiarrhea’ (20). Indeed, stool form can serve asa surrogate marker of gut transit (Table 2) (18-20) and, there-fore, is a reliable indicator of constipation.The importance of large stools: Stool size is important in therecognition, investigation and treatment of constipation. Theclassic 1972 study of stool weight and transit by Burkitt et al(17) found that East Africans had stools five times as heavythat moved twice as quickly through the gut as subjects in theWestern world. He reasoned that the differences were attribut-able to the very high fibre diet of native Africans comparedwith the refined, packaged diet of Europeans. This inverse re-lationship of stool weight and transit time has been confirmedexperimentally (8), as has the ability of increased dietary fibreto increase stool weight and the speed of gut transit (8,22,23).This ability of fibre to increase stool bulk is incompletely under-stood. Fibre has some water-holding properties, but the productsof digestion, gas and quickly absorbed short-chain fatty acidsmay also be important (15,24).

Using plastic stools, Bannister et al (25) showed thatlarger stools are easier for the anorectum to expel than smallstools. This is the scientific basis for the dietary treatment ofconstipation. Clinical data are available and are presented infurther sections (22,23).

PHYSIOLOGICAL CONSIDERATIONSClinically, constipation is defined as a group of functionaldisorders that present as persistent, difficult, infrequent orseemingly incomplete defecation (26,27). However, consti-pation is likely best defined physiologically as delayed transit

156D Can J Gastroenterol Vol 14 Suppl D November 2000

Thompson

TABLE 1Diagnostic criteria for functional constipation*

Two or more of the following for at least three months• Straining at defecation at least one-quarter of the time• Lumpy and/or hard stools at least one-quarter of the time• Sensation of incomplete evacuation at least one-quarter of

the time• Two or fewer bowel movements per week

Abdominal pain is not required, loose stools should not be present, andthere must be insufficient criteria for irritable bowel syndrome. Absence ofstructural, metabolic and pharmacological causes of constipation is im-plied. These criteria may not apply when the patient is taking laxatives.Data from references 6 and 7. *Rome II criteria published in 1999 (see Ap-pendix 1)

TABLE 2The Bristol stool form scale

Type Description

1 Separate, hard lumps like nuts (difficult to pass)

2 Sausage-shaped but lumpy

3 Like a sausage but with cracks on surface

4 Like a sausage or snake; smooth and soft

5 Soft pieces with clear-cut edges (easy to pass)

6 Fluffy pieces with ragged edges; a mushy stool

7 Watery; no solid pieces; entirely liquid

Data from reference 20

through the gut. Thus, transit time is an important consid-eration, and its measurement is an important first step if thesophisticated investigation of recalcitrant constipation isconsidered. Such testing is directed at the detection of a de-fect in colon transit or anorectal function. These defects areuncommon, are difficult to identify positively and are oftenvery complicated to treat. Their investigation is justifiedonly in severely affected patients with prolonged transit timewho are likely to benefit from surgery or biofeedback. First,normal defecation is considered.Optimal conditions for defecation: Physiological informa-tion is available to allow physicians to advise patients abouthow to improve their likelihood of achieving normal defeca-tion. The ‘gastrocolonic response’ is the normal urge to defe-cate after a meal (28). It is hormonally and cholinergically(28,29) mediated; it warns a person to be positioned at thetoilet when it occurs. Usually, this response is best experi-enced after breakfast. Fat (28) and caffeine seem to heightenthe colonic response. Thus, a routine that includes a visit tothe bathroom after a hearty breakfast of bacon and eggs withcoffee may optimize natural responses.

In Western communities, little thought is given to theposition of defecation; we have become adapted to Crap-per’s water closet (30). Our ancestors and most of the worldtoday assume the squat position to defecate (31,32). Physi-ologists point out that this anatomical position optimizesthe attitude of the anorectum and provides the best trajec-

tory for stool. It seems unlikely that patients will reassumethe squat, and modern bathroom designers do not havesuch an eventuality in mind. Nevertheless, this positionmay be mimicked by placing a footstool in front of the toi-let, thus elevating the subject’s thighs and repositioningthe pelvis.

Perhaps the greatest physiological requirement for recal-citrant defecation is time. Precivilized man simply defecatedwhen the urge overtook him. Through centuries of civiliza-tion, social restrictions on the time and place of defecationhave been devised. Modern society does not build defecationinto its daytimers, and the act is often denied or rushed. Theconstipated individual needs to unlearn this unhealthy by-product of ‘evolution’.Transit time: While colonic transit seems a simple concept,it is not. Unlike time trials in the Grand Prix, one cannotsimply swallow a marker and record its arrival at the anuswith a stopwatch. A marker must reflect the properties ofstool. Liquids, large volumes and heavy materials travel fasterthrough the gut. Also, transit is dependent on the consis-tency (14) and specific gravity (9,10) of the intestinal con-tents. Does one measure passage by the beginning point, theend point or the halfway point of a stool? Radiopaque mark-ers have been used with the presumption that they willevenly distribute themselves within the stool and pass alongwith the stool (Figure 1). But when different shaped markersare given for three consecutive days, some of the shapes given


Constipation: A physiological approach

Figure 1) Whole-gut transit. Left Day 0. Twenty-five radiopaque markers have been swallowed and are in the stomach. Right Day 13. The markers havestill not passed through the colon; the patient has a very marked impairment of transit. Note the stool-filled colon. This test should be performed while the sub-ject is on a high fibre diet

on day 3 appear before some given on day 1. Moreover, mark-ers measure whole-gut, not colonic transit time. One couldsubtract the oral-cecal time as determined by a hydrogenbreath test (33); however, that procedure is cumbersome,and the oral-cecal transit time is negligible. A method ofmeasuring whole gut transit is described below.Colon motility: Colon inertia may be diagnosed when, de-spite a high fibre diet, transit is prolonged. Even in specializedcentres, these patients may represent only one-third of consti-pated patients and may include some of those who also haveanorectal dysfunction (34). The increased contact time withthe mucosa increases water absorption, resulting in lumpy andinfrequent stools, straining, and a feeling of incompleteevacuation. Slow transit constipation refers to very slow transitthat is poorly responsive to all therapeutic measures (35,36).

Megacolon is recognized by barium enema and shouldprompt anorectal motility testing to exclude the rare case ofHirschsprung’s disease, especially in children (Figure 2)(37,38). The colonic distribution of transit time markers,intracolonic pressure measurements (at least of the recto-sigmoid) (39) and radioscintography (40) have all been

used to measure colon function but are imprecise. Cer-tainly, subtotal colectomy and ileorectal anastomosisshould not be contemplated until a generalized motility dis-turbance has been excluded by esophageal, gastric andsmall bowel (41) motility tests, and anorectal function isdeemed to be normal (vide infra). Certainly the wise physi-cian will avail himself or herself to the best surgical andmedical opinion available. Some patients have both consti-pation and incontinence because of neurological damageand may benefit from an ileostomy.Anorectal function: Anorectal dysfunction can be suspectedin patients with a full rectum that does not empty despite ex-cessive straining. Some patients digitally assist evacuationthrough the rectum or vagina, or press on their abdomen.When asked to strain, the perineum fails to descend. Unfor-tunately, the relationship of these symptoms to physiologicaltests is inexact (42). Some believe that anismus is character-ized by the collection of transit time markers at the anorectum.The most definitive abnormality is that seen in Hirschsprung’sdisease (37,43,44); here, the denervated internal sphincter failsto relax (Figure 2). While this is a rare abnormality in adults, it isimportant to detect. Surgical remedies are available if the shortdenervated segment can be demonstrated by biopsy. In anismus,the puborectalis sling fails to relax sufficiently to permit the an-orectum to straighten for unimpeded stool passage (Figure 3)(45-48). Defecation is thereby obstructed.

MANAGEMENT OF CONSTIPATIONInitial workup: An initial history and physical examinationshould determine the nature and severity of the constipation,the adequacy of treatments so far, and the presence of morbidconditions that may contribute to the symptoms. Thus, thephysician should inquire about stool frequency, stool form andthe effort required to defecate. Any depression, neuropathy,hypothyroidism, diabetes, drugs (opiates, psychotropics, anti-convulsants, anticholinergics, dopaminergics, calcium chan-nel blockers or bile acid binders) or other possible cause of con-stipation should be noted. Structural disease should beexcluded if suspected. Most patients should have at least a peri-


Thompson

Figure 2) Anorectal manometry measures the internal and external analsphincter response to balloon distension of the rectum. Arrows indicate thetime of balloon distension. A In normal individuals, rectal distension re-flexly relaxes the internal sphincter, while the conscious individual, deem-ing the time for defecation inappropriate, voluntarily tightens the externalsphincter. B In Hirschsprung’s disease, the denervated internal sphincterfails to relax, thus obstructing defecation

Figure 3) Anorectal anatomy. The striated puborectalis muscle pulls therectum forward, creating a sharp anorectal angle. This angle should bemuch less acute during defecation for stool to pass easily. The internalsphincter consists of smooth muscle which contracts involuntarily. Rectaldistension causes the internal sphincter to relax and the external sphincterto contract, preventing precipitous defecation (see Figure 2A).

anal inspection, digital rectal examination and sigmoidoscopy;any patients older than 45 years or at risk of cancer should alsohave a barium enema. Complete testing of blood counts anderythrocyte sedimentation rates should be normal procedure.From there, one can embark on the algorithm proposed in Fig-ure 4. However, there is an exception to the algorithm: if there isreason to suspect Hirschsprung’s disease, especially in children,one must jump directly to anorectal motility testing.

If no other disease is present, the next step is to ensurethat dietary fibre has been tried sufficiently. In primary careand even among patients seeing specialists, most constipa-tion will improve if adequate dietary fibre is given (49,50).The incremental effect of dietary fibre on stool weight isdose-dependent (8,15,22,23,51) and requires a week to reacha steady state (15); this dose effect is weaker in patients withslow-transit constipation (52). Fibre is especially likely to besuccessful if the stools are fragmented, hard or pellety in na-ture. Adequate stool bulk should soften and defragment thestools. Further treatments or tests should not be contem-plated until the physician is satisfied that the constipationwill not improve with some type of dietary fibre.

A true high fibre diet is difficult to achieve. For that reason itis best to introduce fibre supplements. The cheapest and bestsupplement is coarse wheat bran taken by the tablespoon in in-crements until softer stools are more easily passed. Some pa-tients require more than six tablespoons per day; these can betaken in yogurt, cereal, soups or applesauce. Once successful,the patient may integrate the bran into the diet. Fruit and vege-tables are encouraged, but few can achieve sufficient dietary fi-bre intake with these alone. For those who cannot tolerate branor have celiac disease, rice bran, psyllium (53,54) or methyl cel-lulose (55) can be tried. Adequate doses must be taken as theresponse is dose-related. Some psyllium packages recommend adose of a teaspoon, which is often insufficient.

Many patients who are constipated have irritable bowelsyndrome (IBS) (26,27,56). A careful examination of an IBSpatient’s history will reveal an intermittency of constipation,with periods of normal defecation or even diarrhea. WhileIBS patients sometimes benefit from dietary fibre, they willnot benefit from further treatments and testing for consti-pated patients that are described next.

Elderly patients, especially those who have trouble in-gesting bulk, may do well taking an osmotic laxative. Lactu-lose (57), given nightly in one or two tablespoon doses ormore, or a similar dose of milk of magnesia (58), may be useful.

PHYSIOLOGICAL STUDIESMeasurement of transit time: Before proceeding to furthertesting or treatment, a transit time study should be per-formed. A whole-gut transit time test is available for any phy-sician; it is an important determinant of what further actionis justified in the severely affected patient who fails to re-spond to dietary fibre or osmotic laxatives. The markers usedfor transit time measurement may be purchased in capsules(Sitzmark, USA). Each capsule contains 25 radiopaquemarkers. It is good practice to complete a scout film after in-gestion of the capsule to ensure the arrival of the markers in

the stomach and to complete further films on day 3 and day 5.Various formulas have been proposed to establish normaltransit through x-ray examination of the abdomen orthrough examination of each stool (59-61). The acceptednorm is passage of at least 80% of the 25 radiaopaque markersby day 5 (Figure 1). There is debate as to whether one shouldsuspect anorectal dysfunction if the unpassed markers concen-trate in the left colon or rectum (obstructed defecation) (62).

If the transit time is long and the fibre intake is satisfac-tory, then severe constipation is confirmed (Figure 4). Onecan then decide whether to go on to more aggressive treat-ment with polyethylene glycol (PEG), or to test for colon in-ertia or anorectal dysfunction. If, on the other hand, thetransit time is normal, it is difficult to confirm a diagnosis ofsevere constipation, and none of the above investigationsare justified. In such a case, there must be a perception prob-lem requiring patient education or a psychological problem(such as ‘denied defecation’ [56,63]) that requires a psycho-logical assessment.

Only a few centres are equipped to carry out sophisticatedphysiological studies and fewer still have the capability to in-terpret them correctly; hence, a minority of patients benefitfrom the results.Tests for colon inertia: The theoretical importance of dis-covering colon inertia is that such a patient may benefit froma colon resection. The practical reality is that, in the absenceof megacolon, isolated colon inertia is rare. Colon resectionwill have disastrous results if the patient also has anismus ora neuromuscular disturbance that involves other segmentsof the gut (64,65). Nevertheless, in certain patients colon



Figure 4) Simplified approach to chronic constipation. Note that irritablebowel syndrome patients have intermittent constipation, abdominal painand episodes of nonlaxative-induced diarrhea, and are excluded. Eachstep in this scheme should be carefully considered. Transit time measure-ment is only indicated after the lifestyle and dietary changes outlined in thisarticle have truly failed. The decision to do physiological tests in patientswith prolonged transit depends on the likelihood of benefit. If surgery orbiofeedback is out of the question, then such studies are of little use.R/O Rule out

motility can be measured usefully, and there are surgicalsuccesses (66,67).Tests for anorectal dysfunction: Anorectal motility may bemeasured in a variety of ways, but the most readily availabletechnique is by using a device that measures the internal andexternal anal sphincter pressure response to intrarectal bal-loon distension. The most graphic demonstration is throughdefecography (Figure 5) (45-48). Other techniques includetesting the expulsion of plastic stools placed in the rectum (68)and electromyography of the pelvic floor and anal sphincters.Unfortunately, the border between normal and abnormal isindistinct, and surgical management of anorectal dysfunctionhas been largely unsuccessful. Nevertheless, these tests can:first, detect rectal prolapse or a hitherto unrecognized recto-cele; second, if colon resection is contemplated, assure anorec-tal normalcy; and third, set up the physiological parameters forbiofeedback if such treatment is available in the patient’s com-munity (69-71). The technical aspects of anorectal assessmentand treatments are described elsewhere (71,72).

However, there is still much to learn. Symptoms of pelvicfloor dysfunction do not correlate well with physiological tests(73), and no single test can identify whether a patient’s con-stipation is due to IBS, delayed transit or pelvic floor dysfunc-tion (42). While biofeedback is harmless, surgical treatmentsare not. Other than for Hirschsprung’s disease, rectal prolapseor certain rectoceles, anorectal corrective surgery is experi-

mental and should not be attempted without advice fromcentres with sophisticated equipment and expertise.

TREATMENT FOR SEVERECONSTIPATION

Laxative measures: Some patients who have troublesomeconstipation and prolonged transit will have regular defeca-tions when given large doses of an osmotic laxative. PEG issold as a powder to be mixed in a 4 L solution as preparationfor bowel procedures such as colonoscopy (74). It is avail-able in 1 L aliquots and can be given in 300 to 400 mL dailydoses (75,76). While PEG does not restore defecation tonormal, it does generate regular evacuations, which relievesmany patients who have not had regular movements foryears. PEG has a low sodium content and is isosmotic withblood; thus, electrolyte abnormalities are unusual if renaland cardiac function are normal. Nonetheless, the moni-toring of creatinine and electrolyte levels is wise. In pa-tients in whom no other intervention is likely, thistreatment seems to be the best option.

There are reports favouring the use of the gastrokineticagent cisapride (now withdrawn from the Canadian mar-ket) (77,78) and the prostaglandin analogue misoprostyl(79) as treatment for severe constipation, but it is unclearwhether those treated in these studies were controlled forfibre intake. While these products cause diarrhea in thosewho are not constipated, anecdotal and other evidence sug-gest that they are ineffective in those who are truly consti-pated (80). Neither drug is without risk, and their chronicuse by pregnant (81) or elderly individuals in whom druginteractions are likely is unwise (82).

Many patients select their own laxatives; these may in-clude bisacodyl, anthrocene drugs (senna or cascara) or regu-lar enemas. Sometimes these laxatives are satisfactory andthe patient is reluctant to abandon the treatment. However,many gastroenterologists are concerned that these stimulantsmay, over time, damage the colon (80) and cause electrolytedisturbances (56,63). Soap enemas are potentially dangerous.Surgical measures: Surgical procedures on the colon andrectum are the province of the few experts and centres thatare equipped to handle the selection of suitable patients, aswell as the psychological and physiological issues that theypresent. Surgery should not be performed without expertmedical and surgical opinion. Inappropriate colectomy, ile-ostomy or especially anorectal surgery may leave the patienteven more severely disabled.Other measures: For anismus, some experts recommend bio-feedback (69,71). With this technique, technology is employedto train patients with anismus to relax their puborectalis muscleas they try to defecate. Few centres claim success with thistechnique, which is not easy to apply correctly.

Many patients seek the help of practitioners of alternativemedicine or colon laundries. If patients are satisfied with thesemeasures and medical measures have been unsatisfactory,then the physician’s duty is confined to ensuring the safety ofthe treatments being administered. After all, Louis XIV availedhimself to daily enemas, and he ruled France for 72 years (56).


Thompson

Figure 5) Defecography. Thick barium has been injected into the rec-tum, demonstrating the anorectal angle held in position by a contractingpuborectalis muscle (see Figure 3). This muscle must relax for stool toeasily pass. Failure to relax may obstruct defecation

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31. Straining, sitting and squatting at stool. Lancet 1975;ii:18-9.32. Ogilvie H. The large bowel and its functions. Proc R Soc Med

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46. Wald A, Camara BJ, Freimanis MG, Bauman DH, Hinds JP.



APPENDIX 1Rome II criteria for constipation

In the preceding 12 months, at least 12 weeks (that do not need tobe consecutive) having two or more of:

• Straining at defecation more than one-quarter of the time

• Lumpy or hard stools at defecation more than one-quarterof the time

• Sensation of incomplete evacuations more than one-quarterof the time

• Sensation of anorectal obstruction or blockage at defecationmore than one-quarter of the time

• Manual manoeuvres to facilitate defecation more thanone-quarter of the time (eg, digital evacuation, support ofthe pelvic floor)

• Less than three defecations per week

Loose stools should not be present, and there must be insufficient cri-teria for irritable bowel syndrome. Adapted from references 26 and 27.

Contribution of evacuation proctography and anorectal manometry tothe evaluation of adults with constipation and defecatory difficulty.Dig Dis Sci 1990;35:481-7.

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55. Hamilton JW, Wagner J, Burdick BB, Bass P. Clinical evaluation ofmethylcellulose as a bulk laxative. Dig Dis Sci 1988;33:993-8.

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59. Evans RC, Kamm MA, Hinton JM, Lennard-Jones JE. The normalrange and a simple diagram for recording whole gut transit time.Int J Colorectal Dis 1992;7:15-7.

60. Metcalf AM, Phillips SF, Zinsmeister AR, MacCarty RL, Beart RW,Wolff BG. Simplified assessment of segmental colonic transit.Gastroenterology 1987;92:40-7.

61. Schindlbeck NE, Klauser AG, Muller-Lissner SA. [Measurement ofcolon transit time]. Z Gastroenterol 1990;28:399-404.

62. Kuijpers HC. Application of the colorectal laboratory in diagnosisand treatment of functional constipation. Dis Colon Rectum1990;33:35-9.

63. Thompson WG. Laxative abuse. In: Tytgat GNJ, van Blankenstein M,eds. Current Topics in Gastroenterology and Hepatology. New York:Springer-Verlag, 1990:236-45.

64. Vasilevsky A, Nemer FD, Balcos EG, Christenson CE, Goldberg SM.Is subtotal colectomy a viable option in the management of chronicconstipation? Dis Colon Rectum 1988;31:679-81.

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75. Klauser AG, Muhldorfer BE, Voderholzer WA, Wenzel G,Muller-Lissner SA. Polyethylene glycol 4000 for slow transitconstipation.Z Gastroenterol 1995;33:5-8.

76. Andorsky RI, Goldner F. Colonic lavage solution (polyethylene glycolelectrolyte lavage solution) as a treatment for chronic constipation: adouble-blind, placebo-controlled study. Am J Gastroenterol1990;85:261-5.

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78. Chokhavatia S, Phipps T, Anuras S. Comparative laxation of calciumpolycarbophil with psyllium mucilloid in an ambulatory geriatricpopulation. Curr Ther Res Clin Exp 1988;44:1013-9.

79. Soffer EE, Metcalf A, Launspach J. Misoprostol is effectivetreatment for patients with chronic constipation. Dig Dis Sci1994;39:929-33.

80. Muller-Lissner SA. Adverse effects of laxatives: facts and fiction.Pharmacology 1993;47(Suppl 1):138-45.

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Constipation: A physiological approach - CORE